A checkpoint scheme with task duplication considering transient and permanent faults

Proposed here is a novel architecture for a fault-tolerant real-time system. We employ a checkpoint rollback strategy with double modular redundancy. Main consideration is given to how to recover from both transient and permanent faults without any built-in fault-detection modules or spare processors. Besides state comparison between duplicated tasks, the system has access to the state of the previous checkpoint so that the integrity of a processor can be checked. Using a Markov model capturing the behavior of the proposed scheme, we calculate the probability of task completion against faults that occur in a Poisson process. The optimal number of checkpoints is selected so as to maximize the probability of task completion.